Conventional integrated circuits suffer from numerous reliability and degradation issues. For deep submicron (DSM) designs issues such as hot carrier injection (HCI), time dependent dielectric breakdown (TDDB), negative bias thermal instability (NBTI) and the like, increasingly affect performance of integrated circuits.
In order to increase the performance of an integrated circuit various operating parameters, such as the supply voltage, operating frequency, back bias (e.g., threshold voltage), and/or the like, may be changed. However, there is typically a tradeoff between performance and lifetime of the integrated circuit. Changing the operating parameters to achieve increased performance typically results in an increase in stresses, such as negative bias thermal instability (NBTI). The tradeoff between performance and lifetime may be optimized if NBTI in the integrated circuit can be measured.